1. Field of the Invention
The invention relates to an image emphasizing device which clarifies a two-dimensional pictorial image data and fingerprint image data.
2. Description of Prior Art
In an individual identification device, features are derived from a fingerprint image based on end points and bifurcation points of fingerprint ridge lines when putting a finger tip on an extraction prism. The derived features are stored in a memory as a registration data. Unknown features from an entrant are collated with an already stored features to verify whether or not the entrant is identified.
Upon reading the fingerprint image, it is necessary to attain a well-contrasted fingerprint image particularly when selecting the number of the ridge lines and a positional relationship between the end points of the ridge lines or the bifurcation points of the ridge lines.
When the finger tip gets chappy in a dry season, the ridge lines of the fingerprint image becomes lean and blurred in some places due to a poor contact relation between the finger tip and the extraction prism at the time of putting the finger tip on the extraction prism. This means that the fingerprint image is qualitatively influenced depending on the circumstances under which the fingerprint is taken. This significantly deteriorates a collating accuracy.
Therefore, the present invention has been made with the above drawbacks in mind, it is a main object of the invention to provide an image emphasizing device which is capable of reproducing a clear image by emphasizing an obscure portion of an original pictorial image.
According to the present invention, there is provided an image emphasizing device in which a Fourier transformation member regards a two-dimensional original pictorial image as a time series data to treat the two-dimensional original pictorial image with a Fourier transformation in different directions so as to determine Fourier coefficients in the same directions. This permits to process the original pictorial image within a frequency range.
A weight member puts weight on the Fourier coefficients along the different directions to emphasize an obscure portion of the original pictorial image.
The weighted Fourier coefficients along the different directions are treated with an inverse Fourier transformation to determine corresponding minute amplitude value emphasis data. A synthesizing member synthesizes the corresponding minute amplitude value emphasis data to determine an image data in which the minute amplitude value is emphasized.
Upon applying to a fingerprint verification device, a clear fingerprint image is insured in which the obscure portion is rectified to identify the entrant with a high accuracy. Upon applying to a read-out of an automobile license plate number, a clarified license plate number image is insured in which the obscure portion is rectified to identify the license plate number with a high accuracy.
Depending on the direction in which the original pictorial image is treated with the Fourier transformation, information from the fingerprint ridge lines may be subjected to an attenuation. By synthesizing the data in different directions, the attenuation is suppressed effectively.
According to another aspect of the invention, the different directions are represented by two lines met at right angles. This also suppresses the attenuation effectively.
According to still another aspect of the invention, the different directions are represented by a longitudinal line (y-axis direction) and a latitudinal line (x-axis direction) of the original pictorial image. This not only suppresses the attenuation,but also eliminates the necessity of implementing coordinates transformation substantially. With a common analysis size applied herein, the verification is implemented at a higher speed.